Woven synthetic scrims are now widely used as the primary backing material for tufted carpeting, and scrims woven from polypropylene ribbon filaments are probably the most common. While such scrims have a number of desirable characteristics, they also present some problems. The finished product may not, for example, have suficient dimensional stability, it may not have desirable stiffness, or it may not meet current standards for flame retardance. Another problem is that woven synthetic scrims can be difficult to tuft through because the scrim filaments are likely to slide over one another during the tufting process.
To provide the desired dimensional stability and stiffness for products of the type contemplated, it is common to provide a secondary backing such as jute or a foam layer, but this presents several disadvantages. First, the use of a secondary backing obviously increases material and manufacturing costs. Further, conventional secondary backings reduce the porosity of the finished product so that it holds more liquid and is, for example, less desirable for outdoor use. Still further, conventional secondary backings tend to reduce the flame retardance of the finished product, at least as measured by tunnel test.
NON-WOVEN STAPLE FIBERS HAVE BEEN USED WITH SYNTHETIC SCRIMS, OR TO FORM PRIMARY BACKING MATERIALS, BUT HAVE NOT HERETOFORE BEEN USED IN THE WAY CONTEMPLATED BY THIS INVENTION. In U.S. Pat. No. 3,605,666, dated Sept. 20, 1971, for example, a relatively thin non-woven layer is applied to the top of a woven synthetic scrim; but it serves primarily an esthetic function by providing a dyeable subface. In U.S. Pat. 3,817,817, dated June 18, 1974, a needlebonded layer is applied to the underside of a woven synthetic scrim to make a secondary backing material. In U.S. Pat. No. 2,706,324, dated Apr. 19, 1955, staple fibers are needled onto the bottom surface of a tufted carpet after tufting. In U.S. Pat. Nos. 2,810,950, dated Oct. 29, 1957, and 2,866,206, dated Dec. 30, 1958, needled staple fibers are applied to a fabric, but the fabric appears to serve primarily as a carrier for the fibers, as opposed to providing substantial dimensional stability in its own right, so that the resulting product is essentially a non-woven backing.